The invention relates generally to sensors, and specifically to systems for detecting fugitive emissions.
Federal, state and local air quality compliance regulations have been promulgated to control fugitive emissions from petroleum production, refining and distribution facilities along with petrochemical facilities including refineries, pumping stations, storage facilities, etc. For example, Rule 1173 of the South Coast Air Quality Management District relates to Fugitive Emissions of Volatile Organic Compounds, and has monitoring, record keeping, and reporting requirements. Similarly, Federal Regulations under 40 C.F.R. .sctn.60.105 and 60.107 are another emission standard that impose monitoring, recording, and reporting requirements on petrochemical facilities (but for different constituents).
In general, these regulations require that each possible point of escape for hydrocarbons ("release point") in a facility be identified, monitored, and tracked. Thus, each fitting, joint, packing gland, flange, and other possible release point must be monitored and tracked. Leak limits have been established--if emissions from a source exceed the limit, corrective action must be taken. For example, a slight leak, but one that exceeds a leak threshold, may be subject to repair within 14 days of detection, while a massive liquid leak may be subject to immediate repair.
Tracking the leak history of an emission source is important because a favorable leak history may qualify that source for a reduced monitoring schedule, while a poor leak history may dictate that the part be replaced, the joint reformed, or other corrective action taken. In addition, local and federal regulators have the power to issue notices of violations if appropriate record keeping and required emissions levels are not maintained.
The data collection industry has recognized the advantages of the elimination of paper records in favor of electronic data collection systems. U.S. Pat. No. 5,099,437 to Weber ("Weber") discloses an electronic data collection system for monitoring and tracking fugitive emissions. As shown in prior art FIG. 1, Weber employs a portable barcode scanner 10 for reading barcodes tags fixed to a release point and for generating a signal representative of the barcode value scanned. A portable data collector 12 is coupled to the scanner and receives from the scanner the bar code identification signals. A portable organic vapor analyzer ("OVA") 16 analyzes vapors sensed by vapor probe 14, which includes an analog gauge for continuously displaying the sensed vapor concentration. An analog voltage signal representative of the sensed vapor concentration is transmitted from the OVA to the portable data collector, where the signal is convened from analog to digital and stored in memory. The portable data collector also includes a display for displaying the sensed emissions data.
In using the Weber system, at each release point, the inspector first scans the bar code identification tag associated with the release point. The inspector then applies the probe to the release point, observes the vapor concentration as displayed on the probe's gauge, and locks the sensed analog signal from the OVA into the data collector, creating and closing an emission data record.
After completing inspection of the desired release points, the data collector is connected to a main computer 18 and the emission data records are uploaded from the data collector to the main computer. The main computer compares the sensed data to a predetermined criterion, and is passed or failed. The main computer updates the inspection history, issues repair schedules or lists for emissions sources that failed. and generates reports.
Although the system disclosed in Weber is an improvement over earlier manual sensing and recording systems, it has several drawbacks and disadvantages. It has four separate components--the barcode scanner, portable data collector, vapor analyzer, and vapor probe, all of which must be connected together and carried by the inspector. Several lines are required to interconnect the components (a sample collection line from the probe to the OVA and electrical data lines from the OVA to the dam collector, from the scanner to the data collector and from the OVA to the analog meter). Each line has a connection at each end that is a potential failure point. Each electrical connection must also meet stringent safety requirements, such as intrinsically safe standards for Class I, Division I Group A-D hazardous environments.
The number of components and interconnection lines also renders Inspection of release points cumbersome and inefficient. The inspector must first use the scanner to read the identification bar code, then release the scanner and apply the probe to the release point, observing the reading on the probe's meter. Then, the inspector must lock the sensed reading into the data collector. The separate handling and coordination of the different components complicates the inspection process.
Further, the Weber system does not provide the inspector with on-site guidelines or suggestions for possible repairs. Instead, analysis of the data is performed by the main computer 18, which generates repair instructions for each release point based on the results of the analysis. Thus, a second trip to each release point is always required to repair the leaking part. In the interim between the first visit for emissions measurement and the second visit for repair, the release point has continued to release hydrocarbons into the atmosphere.
The assignee of the present application has used an apparatus similar to the Weber system, except that the portable data collector includes a keyboard to permit the inspector to enter dam, and a separate analog-to-digital converter is disposed in-line between the OVA and the dam collector to convert the analog signal from the OVA to a digital signal usable by the data collector.